package org.richin.crypto.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * 使用java.security.MessageDigest类写的一个工具类用来获取MD5码
 * @author Talen
 * @see java.security.MessageDigest
 */
public class MD5Util {
	/**  
	* 默认的密码字符串组合，apache校验下载的文件的正确性用的就是默认的这个组合  
	*/  
	protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9','a', 'b', 'c', 'd', 'e', 'f' };   
	protected static MessageDigest messagedigest = null;   
	static{   
	   try{   
	    messagedigest = MessageDigest.getInstance("MD5");   
	   }catch(NoSuchAlgorithmException nsaex){   
	    System.err.println(MD5Util.class.getName()+"初始化失败，MessageDigest不支持MD5Util。");   
	    nsaex.printStackTrace();   
	   }   
	}   
	  

	/**
	     * 向getMD5方法传入一个你需要转换的原始字符串，将返回字符串的MD5码
	     * @param code 原始字符串
	     * @return 返回字符串的MD5码
	     */
	public static String getMD5(String code) throws Exception {
		MessageDigest messageDigest = MessageDigest.getInstance("MD5");
		byte[] bytes = code.getBytes();
		byte[] results = messageDigest.digest(bytes);
		StringBuilder stringBuilder = new StringBuilder();

		for (byte result : results) {
			//将byte数组转化为16进制字符存入stringbuilder中
			stringBuilder.append(String.format("%02x", result));
		}

		return stringBuilder.toString();
	}
	/**  
	* 适用于上G大的文件  
	* @param file  
	* @return  
	* @throws IOException  
	*/  
	public static String getFileMD5String(File file) throws IOException {   
	   FileInputStream in = new FileInputStream(file);   
	   FileChannel ch = in.getChannel();   
	   MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());   
	   messagedigest.update(byteBuffer);   
	   return bufferToHex(messagedigest.digest());   
	}   
	private static String bufferToHex(byte bytes[]) {   
		   return bufferToHex(bytes, 0, bytes.length);   
		}   
		  
		private static String bufferToHex(byte bytes[], int m, int n) {   
		   StringBuffer stringbuffer = new StringBuffer(2 * n);   
		   int k = m + n;   
		   for (int l = m; l < k; l++) {   
		    appendHexPair(bytes[l], stringbuffer);   
		   }   
		   return stringbuffer.toString();   
		}   
		  
		  
		private static void appendHexPair(byte bt, StringBuffer stringbuffer) {   
		   char c0 = hexDigits[(bt & 0xf0) >> 4];   
		   char c1 = hexDigits[bt & 0xf];   
		   stringbuffer.append(c0);   
		   stringbuffer.append(c1);   
		}   
		  
		public static boolean checkPassword(String password, String md5PwdStr) {   
		   String s = getMD5String(password);   
		   return s.equals(md5PwdStr);   
		}   
		public static String getMD5String(String s) {   
			   return getMD5String(s.getBytes());   
			}   
			  
			public static String getMD5String(byte[] bytes) {   
			   messagedigest.update(bytes);   
			   return bufferToHex(messagedigest.digest());   
			}   
	/** */
	/**
	     * main方法用于测试
	     */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		//字符'a'的MD5码是0cc175b9c0f1b6a831c399e269772661,如果是，则成功。
		try {
			System.out.println(MD5Util.getMD5("a"));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}
